(1) Field of the Invention
The present invention generally relates to feedback signal stabilization techniques and more particularly to the signal stabilization of an optical hydrophone system that uses two interfering light beams to form a fringe pattern.
(2) Description of the Prior Art
Optical hydrophones using interferometry with homodyne detection are very sensitive devices for detecting acoustic signals. When optical fibers are used for guiding a laser light, such hydrophones can operate at large distances from the light sources or data processing equipment. In practical applications, however, the prior art systems have problems associated with them. One of the problems is the signal stability, because relative phase stability between two interfering beams of the interferometer is required. The phase might be affected by fluctuations in temperature, static pressure, vibrations, etc. A second problem is the need for a known phase relation between hydrophones put in an acoustic array. Acoustic arrays are normally used for improving sensitivity and provide directionality of the signal source, where hydrophones are connected together with a known phase relationship, called beamforming. In optical hydrophones the phase relationship must be established.